U.S. patent number 6,288,174 [Application Number 08/981,806] was granted by the patent office on 2001-09-11 for powdery material and modifier for cementitious material.
This patent grant is currently assigned to Mitsubishi Rayon Co., Ltd.. Invention is credited to Yukihiro Ikegami, Toshihiro Kasai.
United States Patent |
6,288,174 |
Ikegami , et al. |
September 11, 2001 |
Powdery material and modifier for cementitious material
Abstract
An acrylic polymer powdery material, which is a particularly
useful powdery material as a modifier for cementitious material,
comprising fine particles of a core-shell structure comprising a
core polymer being comprised of an acrylic polymer having a glass
transition temperature (Tg) of -20-+15.degree. C., a weight average
molecular weight of 100000-2000000, an acid value of 25 mg KOH/g or
less and a shell polymer being comprised of an acrylic polymer
having a Tg of 50-90.degree. C., a weight average molecular weight
of 100000-2000000, an acid value of 30-130 mg KOH/g, wherein the
weight ratio of the core polymer and shell polymer is 30/70-80/20
(% by weight).
Inventors: |
Ikegami; Yukihiro (Nagoya,
JP), Kasai; Toshihiro (Nagoya, JP) |
Assignee: |
Mitsubishi Rayon Co., Ltd.
(Tokyo, JP)
|
Family
ID: |
26381852 |
Appl.
No.: |
08/981,806 |
Filed: |
February 16, 1999 |
PCT
Filed: |
July 04, 1996 |
PCT No.: |
PCT/JP96/01855 |
371
Date: |
February 16, 1999 |
102(e)
Date: |
February 16, 1999 |
PCT
Pub. No.: |
WO97/03112 |
PCT
Pub. Date: |
January 30, 1997 |
Foreign Application Priority Data
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|
|
|
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Jul 7, 1995 [JP] |
|
|
7-172526 |
Feb 6, 1996 [JP] |
|
|
8-042206 |
|
Current U.S.
Class: |
525/301;
523/201 |
Current CPC
Class: |
C04B
24/2641 (20130101); C04B 24/2688 (20130101); C08F
265/04 (20130101); C08F 265/06 (20130101); C08J
3/12 (20130101); C08F 265/06 (20130101); C08F
2/22 (20130101); C08J 3/126 (20130101); C04B
2103/0058 (20130101); C04B 2111/76 (20130101); C08J
2333/12 (20130101) |
Current International
Class: |
C04B
24/00 (20060101); C04B 24/26 (20060101); C08J
3/12 (20060101); C08F 265/00 (20060101); C08F
265/06 (20060101); C08F 265/04 (20060101); C08F
265/02 () |
Field of
Search: |
;525/301 ;523/201 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
0510805 |
|
Oct 1992 |
|
EP |
|
2-129266 |
|
May 1990 |
|
JP |
|
3-210336 |
|
Sep 1991 |
|
JP |
|
5-112655 |
|
May 1993 |
|
JP |
|
5-140325 |
|
Jun 1993 |
|
JP |
|
6-179754 |
|
Jun 1994 |
|
JP |
|
Primary Examiner: Michl; Paul R.
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner L.L.P.
Claims
What is claimed is:
1. An acrylic polymer powdery material comprising fine particles of
a core-shell structure formed of: (i) a core polymer containing an
acrylic polymer having a glass transition temperature (Tg) of
-20-+15.degree. C., a weight average molecular weight of
100000-2000000, an acid value of 25 mg KOH/g or less; and (ii) a
shell polymer containing an acrylic polymer having a Tg of
50-90.degree. C., a weight average molecular weight of
100000-2000000, an acid value of 30-130 mg KOH/g, wherein the
weight ratio of the core polymer of the shell polymer is
30/70-80/20 (% by weight), the powdery material being free-flowing
and devoid of any secondary aggregated powder crumbs of 1 mm or
greater in diameter.
2. A powdery material as set forth in claim 1, wherein a volume
average particle size of primary particles being within the range
of 200-700 nm, the primary particles comprising a shell polymer
having a glass transition temperature (Tg) 55-80.degree. C. and
having a weight average molecular weight of 300000-1.3 million.
3. A powdery material as set forth in claim 1 or claim 2, wherein
the powdery material has a friability of not less than 50%
according to a blocking test of the acrylic polymer powdery
material conducted under the following conditions: 20 g of sample
is packed into a cylinder with a 54 mm diameter, to which sample is
applied a 5 kg weight which is left standing for 2 hours at
50.degree. C. to produce a blocked product; then the blocked
product is placed on a sieve with 1 mm mesh-opening and it is
electromagnetically vibrated to crumble for 20 seconds, the amount
of the sample falling through the sieve is measured and the
friability is determined by the following formula ##EQU2##
4. An emulsion obtained by dispersing the fine particles of a
core-shell structure of claim 1 or claim 2 in a aqueous alkali
solution at a 10% by weight solids content, which emulsion has a
minimum film forming temperature of 20.degree. C. or lower.
5. A powdery material as set forth in claim 1 or claim 2, wherein
5-70% of the total amount of carboxylic acids contained in the fine
particles of a core-shell structure in has been neutralized.
6. A powdery material as set forth in claim 5 in which 20-60% of
the total amount of carboxylic acid is neutralized.
7. A powdery material as set forth in claim 1 or claim 2, wherein
the powdery material is obtained by spray drying an emulsion
containing the fine particles of a core-shell structure.
8. A powdery material as set forth in claim 1, wherein the powdery
material is obtained by spray drying an emulsion containing the
fine particles of a polymerized core-shell structure obtained by
emulsion polymerization.
9. A powdery material as set forth in claim 1 or claim 2 in which
the fine particles of the core-shell structure formed of a core
polymer and a shell polymer are formed by polymerization from
monomer mixtures having the following compositions:
wherein the core-polymer-forming monomer contains,
(a-1) 90-100% by weight of at least one vinyl monomer selected from
alkyl (meth) acrylates, styrene, vinyl chloride, and vinyl acetate
and
(a-2) 0-10% by weight of one other copolymerizable monomer; and
wherein the shell-polymer forming monomer contains,
(b-1) 70-95% by weight of at least one vinyl monomer selected from
alkyl (meth)acrylate, styrene, vinyl chloride, and vinyl
acetate,
(b-2) 5-30% by weight of an unsaturated carboxylic acid, and
(b-3) 0-10% by weight of one other copolymerizable monomer.
10. A powdery material as set forth in claim 2 in which the fine
particles of a core-shell structure are obtained by a first
polymerization stage of obtaining a core polymer from a
core-polymer-forming monomer by emulsion polymerization and a
second polymerization stage of obtaining a shell polymer from a
shell polymer forming monomer by emulsion polymerization.
11. a powdery material as set forth in claim 9 in which the core
polymer is a polymer having a composition containing 20-70% by
weight of methyl methacrylate, 0-10% by weight of butyl
methacrylate and/or ethyl methacrylate, 30-70% by weight of butyl
acrylate and/or ethyl acrylate and the shell polymer contains
35-80% by weight of methyl methacrylate, 10-40% by weight of butyl
acrylate and/or ethyl acrylate, and 10-25% by weight of methacrylic
acid.
12. A powdery material as set forth in claim 4 in which the minimum
film forming temperature is 5.degree. C. or less.
13. A powdery material as set forth in claim 7 in which the
emulsion contains no anti-blocking agent.
14. A powdery material as set forth in claim 3 in which the
friability is not less than 50%.
15. A powdery material as set forth in claim 3 in which the
friability is about 80%.
16. A modifier for cementitious material wherein an effective
amount of a powdery acrylic polymer material as set forth in claim
1 or 2 is mixed therewith.
Description
TECHNICAL FIELD
The powdery material of this invention is a core-shell structured
powder comprising a core polymer and a shell polymer, and is
particularly effective when used as a modifier for cementitious
material.
BACKGROUND TECHNOLOGY
Cement compositions (hereafter "cement milks") have been mixed with
cement modifying resin materials as cement modifiers, such as
natural rubber, styrene-butadiene latex, acrylonitrile-butadiene
latex, chloroprene latex, and the like, and have been in commercial
use to improve the strength or the like of the concrete products
obtained from such cement milks.
These cement modifiers are roughly classified into aqueous
emulsion-type materials (hereafter "emulsion type cement
modifiers"), and resin powdery materials (hereafter "powdery
material type cement modifiers").
These cement modifiers are required to have the following basic
properties:
1) Good mixing and dispersion stability when the cement modifier is
stirred and mixed with cementitious material;
2) Minimal change in viscosity when incorporated into a cement
milk, with a good workability;
3) Substantial improvement effect on physical properties such as
the strength of the concrete products obtained by hardening the
cement milk, such as surface hardness, compression strength, and
flexural strength (hereafter, "strength"), and adhesion to a
variety of substrates (hereafter "adhesion").
The extent of such improvement in strength, adhesion, and the like,
of concrete products is, in general, said to depend on the glass
transition temperature (hereafter "Tg") of the cement modifier and
its minimum film forming temperature (hereafter "MFT").
Definition: The MFT is the temperature at or above which the
polymer emulsion forms a continuous film. MFT is based on an
apparatus based on the temperature gradient method described by
Protzman and Brown (J. Appl. Polymer Sci 4, (1960)).
Apparatus for Measurement: An emulsion is filled into grooves, 15
mm wide, about 1 mm deep, and 400 mm long on a thick aluminum slab
where a temperature gradient is maintained usually 20-80.degree.
C., and is left standing for several hours. The aluminum slab has
thermocouples embedded at about 25 mm intervals apart; as the water
is allowed to gradually evaporate, a continuous film (or continuous
films) begins to form starting from the high temperature end. The
temperature at which a clear continuous film becomes discontinuous
(formation of cracks and transportation into white powdery state)
is recorded as the MFT.
A cement milk which uses an emulsion type cement modifier
containing a high Tg polymer as an emulsion type cement modifier
has a high MFT and requires a high temperature for hardening into a
concrete product; in particular, when one casts during winter
periods at temperatures lower than the MFT of the cement milk, a
continuous film cannot be formed efficiently when a concrete
article is made, hence, not only is it difficult to produce a
concrete product retaining excellent strength, but there are
sometimes adverse effects on the concrete products in other areas
such as resistance to water, weathering resistance, resistance to
acid, and the like (hereafter summarily called "durability") or in
poor trowelability.
Consequently, it has heretofore been customary to improve the
strength and adhesion of a concrete product by producing it from a
cement milk containing an emulsion type cement modifier having a
lower Tg polymer or a lower MFT.
From among these cement modifiers, powdery type cement modifiers
are superior to emulsion type cement modifiers in that (1) their
transport is easier in that it is not necessary to transport water
as in the case of the emulsion type modifiers and they can be
transported in bags, simplifying packaging; (2) they are easier to
handle in that they do not suffer from freezing or phase separation
as with the emulsion type modifier; (3) they give good workability
and provide concrete products with no performance variations since
a cement milk can be prepared by transporting a cement mixture
obtained by premixing cementitious material with a cement modifier
and simply adding water to the cement mixture at the work site to
produce the cement milk.
However, a cement milk mixed with a powdery material obtained from
a spray dried emulsion having a low Tg or low MFT as described
above, if cast and hardened into a concrete product at low
temperatures such as in a casting application in winter periods,
cannot realize strength and adhesion at satisfactory levels; thus,
low temperature-usable powdery material type cement modifiers have
not yet been discovered.
Powdery type cement modifiers have been proposed, for example, a
powdered cement modifier as described in U.S. Pat. No. 4,916,171,
which is a spray dried powder of an emulsion containing core-shell
structured acrylic polymer particles comprising a core polymer
composed of an alkali insoluble emulsion polymer and a shell
polymer composed of an alkali soluble emulsion polymer, part of
which has been alkaline-neutralized.
The polymer which constitutes the shell of the core-shell
structured acrylic polymer particles disclosed in U.S. Pat. No.
4,916,171 has a Tg of 100.degree. C. or higher and has a high acid
value by virtue of having a large amount of MAA, as high as 20-50%
by weight, copolymerized therein, where the polymer is neutralized
to 80% or higher and has a molecular weight of 5000-50000 so as to
achieve the dispersion stability of the polymer particles in the
aqueous emulsion. However this product has been deficient in that
the polymer constituting the shell of said polymer particles has
the low molecular weight of 5000-50000, resulting in a concrete
product which, after a cement milk containing such a polymer is
hardened, is poor in durability, particularly in resistance to
water, weathering resistance, and resistance to acid; production of
polymer particles by spray drying such an emulsion using a spray
drying process generates polymer particles which tend to block,
whereby the blocked [caked] polymer particles are poor in
friability, making them extremely difficult to handle.
In addressing these problems, U.S. Pat. No. 4,916,171 discloses a
method of adding an anti-blocking agent such as inorganic particles
like fine silica particles to the emulsion and spray drying,
thereby attempting to prevent the resultant polymer particles from
blocking, but polymer particles obtained by such a method end up
containing a large amount of inorganic particles in the polymer
particles, failing to fully exert advantageous properties as a
cement modifier.
Polymer particles having such a high-acid-value shell polymer used
as a cement modifier in a cement milk, will cause the viscosity to
increase to a high level, reducing casting workability; in
addition, concrete products obtained by hardening such a cement
milk do not exhibit sufficient improvements in durability,
strength, adhesion, and the like, so that such a polymer will not
make a satisfactory cement modifier.
In addition, the polymer which constitutes the shell of these
polymer particles a Tg as high as 100.degree. C. or higher so that
a cement milk to which have been added said polymer particles of a
high Tg shell polymer will show a high MFT, thereby showing
inferior curing behavior and failing to provide the resultant
concrete product with properties such as satisfactory durability,
strength, adhesion, or the like, where such shortcomings are
aggravated among other deficiencies when concrete products are
produced, particularly at low temperatures as in winter.
DISCLOSURE OF THE INVENTION
The present inventors intensively studied a way to overcome the
deficiencies of acrylic polymer particles having such prior art
core-shell structures, and as a result, discovered that a powdery
acrylic polymer material capable of solving the above problems can
be obtained by using core-shell structured fine particles having as
a shell polymer an acrylic polymer with Tg 50-90.degree. C., a
weight average molecular weight of 100000-2000000, and an acid
value of 30-130 mg KOH/g; and thus have completed this
invention.
That is, the powdery material of this invention comprises fine
acrylic polymer particles of a core-shell structure comprising a
core polymer comprising an acrylic polymer having a Tg of
-20-+15.degree. C., a weight average molecular weight of
100000-2000000, and an acid value of not higher than 25 mg KOH/g
and a shell polymer of an acrylic polymer having a Tg of
50-90.degree. C., a weight average molecular weight of
100000-2000000, and an acid value of 30-130 mg KOH/g, wherein the
volume average particle size thereof (hereafter simply "average
particle size")is 200-700 nm and the core polymer to shell polymer
ratio by weight is 30/70-80/20 (% by weight).
In addition, the present invention embodies a modifier for
cementitious material obtained by mixing a powdery material
comprising the above-mentioned core-shell structured fine
particles.
BEST EMBODIMENT FOR CARRYING OUT THE INVENTION
The powdery material of this invention and the process for
manufacture thereof will be specifically described below.
[Powdery Material]
The present invention is directed to a powdery material having a
core-shell structure of the aforementioned makeup and a modifier in
which said acrylic powdery material is mixed with cementitious
material.
The powdery material of this invention is obtained by drying by
means of spray drying an a emulsion of fine particles of a
core-shell structure made up of a core of a specific core polymer
and of a shell of a specific shell polymer.
The powdery material of this invention, by virtue of the above
mentioned core-shell structure makeup, provides good film forming
properties at low temperatures for a cement milk added to
cementitious material, which on hardening gives a concrete product
having excellent durability, strength, and adhesion.
Specifically, for the shell polymer which constitutes the powdery
material of a core-shell structure of this invention, raising its
weight average molecular weight enables one to provide
anti-blocking capability when an emulsion in which the fine
particles of the core-shell structure are dispersed is converted to
a powdery material, as well as anti-blocking capability when said
powdery material is stored for a long period of time; at the same
time it provides improved durability to the concrete product
obtained therefrom. With the Tg being in the range of 50-90.degree.
C. and the acid value being in the range of 30-130 mg KOH/g for the
shell polymer, it can provide a powdery product that can realize a
low MFT, with the MFT being at 25.degree. C. or lower, and that has
a suitable alkaline solubility, so that a cement milk to which this
powdery material is added will have a low viscosity and good
casting workability, thereby enabling a hardened concrete product
to be provided with excellent durability and strength.
In addition, the core polymer which constitutes the powdery
material of this invention of a core-shell structure is controlled
to have its acid value to be within a specific range so as to
maintain the dispersion stability of the powdery material in an
aqueous alkali solution and to ensure good film forming capability
for a cement milk containing said powdery material at low
temperatures, particularly at 20.degree. C. or lower, by optimizing
its Tg; in addition, raising its weight average molecular weight
provides the concrete product obtained by hardening the cement milk
to which the powdery material is added with excellent durability
and strength.
It is particularly important for this invention to use as a shell
polymer an acrylic polymer having a Tg of 50-90.degree. C., weight
average molecular weight of 100000-2000000, and an acid value of
30-130 mg KOH/g.
This is because if the shell polymer has a Tg less than 50.degree.
C., the powdery material will undergo blocking to itself when the
powdery material is manufactured by spray drying the emulsion
containing fine particles with a core-shell structure, which will
considerably decrease the powdery material production workability
and productivity, and at the same time that will produce a powdery
material having inferior anti-blocking properties when stored over
a long period of time. On the other hand, a cement milk containing
a powdery material with a shell having a Tg exceeding 90.degree. C.
will have a high MFT, producing a concrete product with reduced
strength, particularly in flexural strength and compressive
strength. Thus, such cement milk will have a substantial drop in
these properties, particularly when cast at low temperatures as in
winter periods. The shell polymer should preferably have a Tg of
50-90.degree. C., more particularly 55-80.degree. C.
A shell polymer with a weight average molecular weight less than
100000 will cause the concrete product obtained from a cement milk
containing such core-shell polymer powdery material to have reduced
durability; in particular, that concrete product will have
substantially decreased durability if such a cement milk is cast at
low temperatures.
In contrast, a core-shell type polymer powdery material having a
weight average molecular weight exceeding 2000000 is not preferred
because it will have an extremely low solubility in aqueous alkali
solution and the cement milk containing such a powdery material
will have too high an MFT and at the same time a substantial
increase in viscosity, reducing casting workability. The weight
average molecular weight of the shell polymer should be in the
range of 100000-2000000, preferably 300000-1.5 million.
The acid value of the shell polymer should be in the range of
30-130 mg KOH/g if it is aimed to reduce the viscosity of the
cement milk containing the powdery material of this invention, to
reduce the MFT, and to strike a good balance in properties such as
the durability and strength of the concrete product obtained from
such a cement milk. A powdery material having an acid value less
than 30 mg KOH/g will have a shell with a low alkali solubility so
that the core-shell type polymer powdery material in an aqueous
alkali solution will have poor dispersion stability, failing to
sufficiently reduce the MFT of the cement milk containing the
powdery material, thereby resulting in inferior casting
workability.
On the other hand, a core-shell type polymer powdery material
having a shell with its acid value exceeding 130 mg KOH/g will have
a high solubility in aqueous alkali solution so that the cement
milk containing such polymeric powder will considerably increase
its viscosity, thereby lowering casting workability, in addition,
providing the concrete product with reduced durability.
The shell polymer should have an acid value in the range of 30-130
mg KOH/g, preferably 40-120 mg KOH/g.
The shell-polymer that constitutes the powdery material of this
invention, preferably comprises 70-95% by weight of at least one
vinyl monomer (b-1) selected from alkyl (meth)acrylate, styrene,
vinyl chloride, and vinyl acetate and 5-30% by weight of an
unsaturated carboxylic acid (b-2).
For the alkyl (meth)acrylate and the unsaturated carboxylic acid
(b-2) used as a (b-1) vinyl monomer which constitutes the shell
polymer one may use the same type of monomer used in the core
polymer to be described later. The core polymer of this invention
comprises an acrylic polymer having its Tg in the range of
-20-+15.degree. C. weight average molecular weight of
1000000-2000000, and an acid value of 25 mg KOH/g from the
standpoints of stably dispersing the powdery material of this
invention in aqueous alkali, without being dissolved and of
ensuring the film-forming capability of a cement containing the
powder material of this invention at 20.degree. C. or lower, and of
improving the durability and strength of the concrete product to be
obtained therefrom.
The core polymer should have average Tg's in the range of
-20-+15.degree. C. in order to improve the film forming capability
of an emulsion containing the powdery material of this invention,
particularly so as to reduce its MFT at low temperatures.
Setting the Tg of the core polymer to be at +15.degree. C. or lower
can reduce the MFT of the cement milk containing the powdery
material of this invention to 20.degree. C. or lower, which can
then provide good workability even at low temperatures such as in
winter castings, at the same time, enabling one to produce a
concrete with good durability and strength and free from crack
formation or the like.
Setting the Tg of the core polymer to -20.degree. C. or higher can
provide a powdery material with excellent anti-blocking properties
both during spray drying an emulsion containing fine particles with
a core-shell structure resulting from emulsion polymerization and
during its long storage time.
The core polymer preferably has its weight average molecular weight
in the range of 100000-2000000 so as to improve the properties of
the concrete product obtained from a cement milk containing the
powdery material of this invention, particularly for improved
durability at low temperatures such as resistance to water,
weathering resistance, resistance to acid, and the like.
In addition, it is preferred for the acid value of the core polymer
to be in a range not more than 25 mg KOH/g for reducing the
solubility of the powder in the cement milk, to which the powder of
this invention is added, and at the same time suppressing the
increase in viscosity of the cement milk, thereby providing good
workability.
The core polymer of this invention comprises an acrylic polymer
obtained by polymerizing a monomer mixture of 90-100% by weight of
at least one vinyl monomer (a-1), selected from alkyl (meth)
acrylates, styrene, vinyl chloride, and vinyl acetate, 0-5% by
weight of an unsaturated carboxylic acid (a-2), and 0-5% by weight
of one other copolymerizable monomer (a-3).
The alkyl (meth) acrylate used as a vinyl monomer (a-1) which makes
up the core polymer includes, for example, methyl (meth) acrylate,
ethyl (meth) acrylate, butyl (meth) acrylate, and the like; the
unsaturated carboxylic acid (a-2), for example, includes
methacrylic acid, acrylic acid, itaconic acid, and the like; and
the other copolymerizable monomer (a-3) includes, for example,
2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate,
2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, and the
like.
The weight ratio of the core polymer to the shell polymer which
make up the fine particles of the core-shell structure of this
invention is preferably in the range of core polymer/shell polymer
(% by weight)=30/70-80/20, preferably in the range of
30/70-70/30.
A shell polymer in the fine particles in an amount less than 20% by
weight will fail to sufficiently cover the low Tg core polymer,
which makes it difficult to obtain fine particles with a complete
core-shell structure so that an emulsion containing such fine
particles will tend to block at the time of spray drying or during
a long term storage of the powdery material, in addition, the
blocked powdery material will tend to be inferior in
friability.
Fine particles with a core shell structure with the shell polymer
content exceeding 60% by weight will have increased solubility in
aqueous alkali solution of the powdery material of this invention
so that the cement milk containing such powdery material will
exhibit the behavior of rapidly increasing viscosity, thereby
tending to have reduced casting workability.
The powdery material of this invention should have 5-70%,
preferably 10-60%, more particularly 20-60%, of the total carboxyl
groups in the fine particles of a core-shell structure
neutralized.
An emulsion containing fine particles of a core-shell structure
with such a high degree of neutralization will exhibit a good spray
state at the time of spray drying, thereby further improving
blocking resistance during the spray drying and during the
long-term storage of the resultant powdery material. Addition of
such a powdery material to an aqueous alkali solution will cause
even secondary aggregates, which are aggregates of primary
particles, to show good friability and further improve dispersion
stability.
A cement milk containing a powdery material comprising partially
neutralized fine particles of this invention can not only impart
the goal properties of this invention such as durability, strength,
and the like, but it can also show improved workability such as in
trowelling and the like, and also can improve the adhesion of the
concrete product prepared from the cement milk to a variety of
substrates.
A powdery material comprising a polymer with a degree of
neutralization less than 5% sometimes may show reduced dispersion
stability in an aqueous alkali solution. In order to improve
workability such as the trowelling of a cement milk containing the
powdery material as well as the durability and strength of the
resultant concrete product, the degree of neutralization of the
polymer particles, which make up the powdery material, is
preferably 5% or higher. Said powdery material obtained from an
emulsion containing a powdery material of a polymer having a degree
of neutralization higher than 70% tends to swell in an aqueous
alkali solution or in a cement milk, or to gel to form an
aggregate, so that the degree of neutralization should be not more
than 70%.
The emulsion containing the powdery material of this invention will
have a low MFT and the cement milk containing this powdery material
will show improved low temperature hardening capability.
When a cement milk having such properties is cast, the formation of
a resin coated film on the surface of the cement milk will prevent
water from evaporating so as to be able to contribute to a
sufficient cure, (that is, a hydration reaction) at the surface
layer of the concrete product, and also will form resin coated
films between the components of the cementitious material, whereby
one can obtain an outstanding concrete product in terms of overall
strength such as surface hardness, flexural strength, compressive
strength, and the like.
The emulsion obtained by dispersing the powdery material of this
invention in an aqueous alkali solution has an MFT not higher than
20.degree. C., preferably not higher than 5.degree. C. so that the
cement milk containing said polymer fine particles will undergo a
good hydration reaction of the cementitious material, thereby one
can obtain a concrete product with further improvement in strength
and durability.
[Process of Manufacturing Powdery Material]
There are two methods for the production of fine particles of a
core-shell structure that constitute the powdery material of this
invention.
One is a process called a seed emulsion polymerization process
which comprises preparing a monomer mixture for a core formation,
carrying out an emulsion polymerization to produce an emulsion
containing the core polymer, preparing a shell-forming monomer
mixture, adding this mixture to the first emulsion, and carrying
out an emulsion polymerization, yielding the shell component.
The other is a process of generating polymer particles of a
core-shell structure, which comprises first preparing a monomer
mixture for generating the shell, emulsion polymerizing this to
produce an emulsion containing the shell polymer, preparing a
monomer mixture for producing the core and adding the mixture to
the first emulsion, and carrying out a phase transition
polymerization.
In particular, the above seed emulsion polymerization method is
preferred in the manufacture of fine particles of a core-shell
structure of this invention in that one can increase the molecular
weight of the shell polymer, which can improve the durability such
as resistance to water, weathering resistance, resistance to acid,
and the like, of the concrete product that can be obtained from a
cement milk containing this powdery material.
For use of the powdery material of this invention as a modifier for
cementitious material, it is particularly preferred to manufacture
the powdery material in the following manner using a seed emulsion
polymerization process:
A monomer mixture for the generation of a core polymer is prepared
which comprises 90-100% by weight of at least one vinyl monomer
(a-1) selected from alkyl (meth) acrylates, styrene, vinyl
chloride, and vinyl acetate, 0-5% by weight of an unsaturated
carboxylic acid (a-2), and 0-5% by weight of a
hydroxyl-group-containing (meth) acrylate , with the total
amounting to 100% by weight, followed by emulsion polymerization to
generate an emulsion in which the core polymer which becomes the
seed particles is dispersed.
Then a monomer mixture for the formation of the shell polymer is
prepared which comprises 70-95% by weight of at least one vinyl
monomer (b-1) selected from alkyl (meth) acrylates, styrene, vinyl
chloride, and vinyl acetate, and 5-30% by weight of an unsaturated
carboxylic acid (b-2), with the total amounting to 100% by weight;
the mixture is sequentially added dropwise, to the emulsion
containing the above core polymer, followed by carrying out an
emulsion polymerization using the seed particles as nuclei thereby
generating a shell polymer to produce an emulsion containing fine
polymer particles with a core-shell structure.
The fine polymer particles of a core shell structure referred to
here are present in the emulsion in a state of primary particles
with an average particle size being about 200-700 nm; if the
average particle size of this core-shell structured fine particle
is smaller than 200 nm, the particle surface area per unit volume
will be higher, resulting in an insufficient thickness of the shell
polymer layer and tending to fail to sufficiently impart
anti-blocking properties during spray drying and during storage; in
addition, the result would be a smaller amount of core polymer per
particle so that these fine particles would tend to be unable to
impart satisfactory durability and strength as a modifier to the
cementitious material. If the average particle size is greater than
700 nm, the emulsion as such will have poor stability, and at the
same time the layer of the shell polymer contained in the primary
particle will be too thick to fully make use of the effect of the
component which imparts lower MFT and lower viscosity, contained in
the core polymer in the fine particles, so that such emulsion will
tend to give a powdery material that cannot satisfactorily meet the
goal performance of this invention.
The resultant emulsion as above, on spray drying, gives the powdery
material of this invention.
The method of spray drying the emulsion containing fine particles
of a core-shell structure is not particularly limited and any
conventional spray dryer can be used; the preferred temperature
conditions for the spray drying should be so selected to increase
the difference in temperature between the emulsion spray inlet of
the spray dryer and the powdery material outlet, which will result
in good drying efficiency for the emulsion resin.
To produce fine particles of a partially neutralized core-shell
structure, the emulsion containing fine particles in the core-shell
structure prepared as above should be neutralized for as much as
5-70% of the total carboxyl groups in said particles by adding
alkali, followed by drying via a spray drying process.
There are no particular limitations as to the alkali types used in
neutralization; one can use alkali metal hydroxides of potassium,
sodium, magnesium, calcium, aluminum, and the like, organic amines
such as ethyl amine, ethanolamine, diethyl amine, pyrrolidine,
triethyl amine, and the like, ammonia, and the like.
Spray drying the above emulsion will give a powdery material with
an average particle size of about 5-100 .mu.m comprising secondary
particles resulting from lightly aggregated primary particles. The
powdery material of this invention refers to primary particles
within the above particle size range or to particles in a mixed
state of primary particles with secondary aggregates with good
friability.
The term "friability" referred to in this invention is evaluated in
terms of the percentage extent of crumbling exhibited by a powdery
material in a blocking test performed under the following
conditions:
[Powdery Material Blocking Test]
A 20 g sample is packed into a cylinder with a 54 mm diameter, to
which sample is applied a 5 kg weight to be left standing for 2
hours at 50.degree. C. to produce a blocked product. Then the
blocked product is placed on a sieve with a 1 mm-mesh opening and
is electromagnetically vibrated to crumble for 20 seconds, thereby
measuring the amount of the sample falling through the sieve.
##EQU1##
The powdery material of this invention should have this friability
being not less than 20%, preferably not less than 50%, more
particularly about 80%.
A product with friability of not more than 50% will cause the
powder to exhibit poor dispersion stability in aqueous alkaline
solution; and when such a powder is used as a modifier for
cementitious material, this will tend to make the various
performance features poorer than those of concrete products using
no such cement modifier.
The powdery material of this invention exhibits excellent
anti-blocking properties because the shell polymer constituting the
fine particles of the core shell structure has a high weight
average molecular weight of 100000-2000000 and exists in a state of
primary particles having the above average particle size or in a
state of a light degree of secondary aggregation of those primary
particles so that the powdery material, when dispersed in an
aqueous alkali solution or the like, is readily dispersed to a
state close to that of the primary particles, thereby fully
realizing its characteristics as fine particles of a core-shell
structure.
Another feature of the powdery material of this invention is that
optimizing the shell polymer's Tg, acid value, and weight average
molecular weight provides very good anti-blocking properties when
the emulsion polymerized solution containing polymer particles of a
core shell structure are spray dried into a powdery material, no
longer requiring an anti-blocking agent such as an inorganic
powdery material or the like.
Therefore, the resultant powdery material is free from any effect
due to the use of anti-blocking agents, free from the poor
dispersion in the emulsion polymerized solution of core-shell type
polymer particles due to the anti-blocking agents such as inorganic
powdery material or the like when blended into cementitious
material, or free from any delay in hardening or any depression in
strength of the cement milk, thereby producing a concrete product
with excellent durability, strength, and clarity as well as a good
surface state.
When the powdery material of this invention is used as a modifier
for cementitious material, the applicable cementitious material is
not particularly limited to any types, including regular hardening
Portland cement, as well as rapid hardening Portland cement, ultra
rapid hardening Portland cement, and the like.
The cement milk containing the powdery material of this invention
can be used in a variety of applications with no limitations, for
use of trowels, base-coats, semi-flexible pavements, or other
special applications regardless of cement milk viscosities, from
low to high viscosities.
EXAMPLES
Hereafter, with reference to working examples, this invention
aisexplained. In these examples, "parts" are "parts by weight";
percentages(%) in these examples are based on % by weight.
The test items of the powdery material of this invention were
measured by the following methods.
[Acid Value]
The amount of KOH in mg needed for neutralizing 1 g of a powdery
material (mg KOH/g).
[Conditions Under which Emulsion is Spray Dried]
The conditions under which the powder was sprayed from the atomizer
outlet was visually inspected.
.smallcircle.: Free of any fused powdery material, with uniform
emulsion spray drying
X: Accumulation of fused powdery product, with uneven emulsion
spray drying
[Anti-blocking Properties]
The state of the powdery material obtained by spray drying an
emulsion was observed under an electron microscope (Nippon Denshi
KK: trade name JSM-5200)
.smallcircle.: A free-flowing powder devoid of any secondary
aggregated powder crumbs reaching 1 mm or greater in diameter
X: A non-free-flowing powdery material with secondary aggregated
powder crumbs of 1 mm or greater in diameter
[Dispersion Stability]
An aqueous alkali solution adjusted to pH 12 by adding 28% aqueous
ammonia to 90 parts of pure water was stirred (150 rpm) by a
"homodisper" to which 10 parts of a powdery material was added and
the mixture was stirred for 5 minutes to obtain an emulsion, and
the way the powder was dispersed in the emulsion was visually
observed.
.smallcircle.: The powder was uniformly dispersed and milky white
in the aqueous alkali solution, free of any aggregates or
precipitates.
.DELTA.: Aggregates and precipitates were observed
X: The powder was partially dissolved in aqueous alkali and showed
the behavior of increased emulsion viscosity.
[Resistance to Water]
10 parts of a powdery material was mixed with aqueous alkali
solution which had been adjusted to pH 12 by adding 28% aqueous
ammonia to 90 parts of pure water to generate an emulsion; and the
emulsion was then cast onto plate glass followed by drying and film
forming; and the resultant film was soaked 24 hours in water to
visually observe the change in the state of the film by visual
inspection.
.smallcircle.: Not dissolved, with essentially no change
.DELTA.: Not dissolved, but with whitening and swelling
X:The film became brittle and was peeled off and/or dissolved and
peeled off.
[Resistance to Acid]
10 parts of a powdery material was converted into a film by the
above casting method and the resultant film was then soaked 24
hours in 5% aqueous hydrochloric acid solution to visually observe
the state of said coated film.
.smallcircle.: Essentially no change
X: The film became brittle, and was peeled off or dissolved and
peeled off.
[Cement Blend Composition A: for Semi-flexible Pavement]
A cement milk was prepared from a ultra rapid hardening Portland
cement/regular Portland cement/gravel powder/powdery
material/water=120 parts/730 parts/80 parts/34 parts/550 parts.
[Cement Blend Composition B: for Trowelling]
A mortar was prepared from Portland cement/sand (Toyoura Standard
Sand)/powdery material/water=100 parts/300 parts/10 parts/70
parts.+-..alpha. parts. The Toyoura Standard Sand is the product
obtained by removing foreign objects from natural silicate sand
produced in Toyoura Cho, Yamaguchi-ken, Japan, and adjusted to a
particle size which would give not more than 1% residue remaining
on a standard 300 .mu.m screen sieve with at least 95% remaining on
a standard 100 .mu.m screen sieve.
[Cement Milk Viscosity]
Cement blend composition A and cement blend composition B were
tested by placing each cement milk in a P funnel and measuring the
time for the milk to flow out, to be used as a measure of
viscosity.
.smallcircle.: At least 10.0 seconds, but less than 11.0
seconds
.DELTA.: At least 11.0 seconds, but less than 12.0 seconds
X: At least 12.0 seconds
[Surface Hardness]
The cement milk of cement blend composition A prepared as above,
was poured into 4 cm.times.4 cm.times.16 cm mold, cured for 1 week
in a constant temperature, constant humidity bath set to a humidity
of 80%, removed from the mold, and the surface was scratched with a
metal spatula to evaluate surface hardness.
.smallcircle.: the surface layer cannot be scraped off.
.DELTA.: part of the surface layer is peeled off.
X: the surface is brittle and can be easily scraped off.
[Trowelability]
A mortar with a cement blend composition B prepared as above, was
coated onto a flat mortar sheet to a 100 mm thickness, and the
finished coating was subjected to a sensory evaluation.
.smallcircle.: a smooth and flat finish
.DELTA.: somewhat sticky or flaky
X: sticky or flaky, difficult to be finished into a smooth
surface.
[Flexural Strength]
The mortar of the cement blend composition B above was filled into
a 4 cm.times.4 cm.times.16 cm mold and cured according to JIS A6203
conditions to give a hardened product, on which three flexural
strength measurements were made using a 1 ton Tensilon to obtain an
average value therefrom.
.smallcircle.: exceeding 45 kgf/cm.sup.2
.DELTA.: 35-45 kgf/cm.sup.2
X: less than 35 kgf/cm.sup.2
[Compression Strength]
The above cement blend composition B mortar was filled into a 4
cm.times.4 cm.times.16 cm mold, and cured according to JIS A6203
conditions to give a hardened product, which was measured 3 times
using a mortar compression test machine by means of a 60 ton
Tensilon and the average values were obtained.
.smallcircle.: exceeding 110 kgf/cm.sup.2
.DELTA.: 90-110 kgf/cm.sup.2
X: less than 90 kgf/cm.sup.2
[Adhesion Strength]
The above cement blend composition B mortar was applied with a
trowel onto a flat mortar sheet to 10 mm thickness and hardened
according to JIS A6203 conditions to give a hardened product;
adhesion strength was measured 3 times using a 1 ton Tensilon, and
an average value was obtained.
.smallcircle.: exceeding 10 kgf/cm.sup.2
.DELTA.: 8-10 kgf/cm.sup.2
X: less than 8 kgf/cm.sup.2
Example 1
A 2 l four-necked flask was charged with 925 parts of pure water,
12.5 parts of polyoxyethylene nonylphenyl ether (manufactured by
Kao KK; trade name Emarugen 910), and 0.75 parts of potassium
persulfate, sparged with nitrogen gas, stirred under a nitrogen gas
stream at 130 rpm, and heated to 70.degree. C.
Then a mixture of 125 parts of methyl methacrylate, 125 parts of
butyl acrylate, and 5.0 parts of polyoxyethylene nonylphenyl ether
(manufactured by Kao KK; trade name Emarugen 905) was added
dropwise to the above flask in 3 hours, and the mixture was held at
70.degree. C. for 1 hour. Then a mixture of 135 parts of methyl
methacrylate, 65 parts of butyl acrylate, 50 parts of methacrylic
acid, and 5.0 parts of sodium dialkyl sulfosuccinate (manufactured
by Kao KK; trade name Perex OTP [phonetic translation]) was added
dropwise to the above flask over 2 hours.
The mixture was held 1 hour at 70.degree. C. and then heated to
80.degree. C. and was held 1 hour at the temperature to complete
the polymerization to give a milky white emulsion polymer (%
solids, 36.2%; weight average molecular weight, 800000).
The resultant emulsion polymer was spray dried using a spray dryer
(manufactured by Ohkawara Kakoki; trade name L-8 Model) set at a
chamber inlet temperature of 130.degree. C. and chamber outlet
temperature of 70.degree. C. with the number of the atomizer
revolutions at 30000 rpm to give a powdery product.
The state of spraying was good and there was no adhesion of the
emulsion polymer and/or its spray dried powdery product to the
inner walls of the chamber and transport tube.
The resultant powdery material had a core polymer with a Tg
(calculated value) of 11.degree. C., a shell polymer with a Tg
(calculated value) of 59.degree. C., an average particle size of 26
.mu.m, and a water content of 1.1%; no blocking of the powdery
material to itself was observed at all.
An observation of the powdery product under an electron microscope
indicated a secondary aggregate of primary particles of an average
particle size of 1 .mu.m or less, forming powders of about 26 .mu.m
in average particle size.
10 parts of the resultant powdery material was placed in aqueous
ammonia with the pH adjusted to 12 by adding 28% aqueous ammonia to
90 parts of water to form an emulsion, which showed a good
dispersion stability of the powdery material, and the emulsion had
an MFT of not higher than 5.degree. C.
The resultant powdery product obtained by the method described
above was used as a modifier for a cementitious material by
uniformly mixing 3 parts of the powdery material with 100 parts of
Portland cement, adding 55 parts of pure water, and well mixing to
prepare a cement milk. The cement milk had a viscosity in terms of
flow time of 10.4 seconds, as measured according to the above
evaluation method.
The cement milk was then cured for 1 week under the above
conditions to evaluate its surface hardness, which showed a good
hardened state with no part of the surface layer of the concrete
product having been scrapped off.
Examples 2-5 and Comparative Examples 1-10
Emulsions containing fine particles with a variety of core-shell
structures were prepared using the compositions given in Table 1
and the same procedure as that of Example 1, followed by spray
drying in a manner similar to that of Example 1 to obtain powdery
materials.
Various evaluations of the resultant powdery materials are given in
Table 1.
However, the powdery materials obtained in Comparative Examples 1,
5, 12, and 15 failed to give powdery products because the fused
emulsion polymer accumulated at the atomizer opening during spray
drying. Therefore, the resultant powders could not be evaluated for
their dispersion stability, the viscosity of the emulsions
containing such powdery material, the MFT of said emulsions, the
viscosity of the emulsion obtained by blending the resultant powder
with cementitious material, or the resistance to water, resistance
to acid, and surface hardness of concrete products obtained by
curing such emulsions.
Examples of this invention and comparative examples are each
described below.
Examples 1-3 showed no blocking of the powdery material to itself,
had good dispersion stability, and gave powdery materials with an
MFT of 5.degree. C. or less. These were blended with a blend
composition given in Table 1 to obtain concrete products which gave
good surface hardness when hardened both at 25.degree. C. (Example
1) and at 5.degree. C. (Example 2).
Example 3 is a case of blending, at a different weight ratio (P/C)
of the powdery material/cementitious material, which gave products
with good states.
Examples 4 and 5 and Comparative Examples 1 and 2 are those of
changing the weight ratios of the core-shell of the powdery
materials.
Examples 4-5 showed no blocking of the powdery materials, gave good
dispersion stability, and yielded powdery products with an MFT of
5.degree. C. When these were used to prepare cement milks with the
blend composition given in Table 1 to generate concrete products,
they gave good concrete products whether hardened at 25.degree. C.
(Example 4) or 5.degree. C. (Example 5).
Comparative Examples 1 and 2 are those of changing the weight
ratios of the core polymer/shell polymer.
Comparative Example 1 failed to produce a powdery material product
because the ratio of the shell polymer was too law which resulted
in a complete blocking during spray drying.
Comparative Example 2 is a case in which the ratio of the shell
polymer was instead increased. In this case, no blocking of the
resultant powdery material to itself was observed and it had a good
re-dispersion capability, but the too high a ratio in the
high-acid-value resin caused a considerable increase in viscosity
when blended into a cementitious material.
Examples 6 and Comparative Examples 6 and 7 are examples in which
the acid value of the shell polymer was varied. Example 6 is a case
where the acid value of the shell polymer was 90 mg KOH/g. It had
an MFT 5.degree. C., which exhibited a good hardened state when
made into a concrete product at 25.degree. C.
Comparative Example 6 is one in which the acid value of the shell
polymer was further reduced to 12 mg KOH/g. In this case, the shell
polymer lost alkali solubility and the MFT did not decrease.
Therefore, this means a poor hardened state would result under
hardening conditions at 25.degree. C.
Comparative Example 7 is one in which the acid value of the shell
polymer was raised to 200 mg KOH/g. In this case, an emulsion
containing the resultant powdery material had a drop in the MFT,
but showed a considerable increase in viscosity when dissolved in
alkali.
Examples 7, 8, and Comparative Example 10 and 11 are those in which
the weight average molecular weight of the core polymer was
varied.
Examples 7 and 8 gave MFTs at 5.degree. C. and gave cement milks
with good properties and concrete products obtained by hardening
the same gave good performance.
However, Comparative Examples 10 is one for reducing the weight
average molecular weight of the core polymer, where the powdery
product obtained did not block and gave an emulsion containing it
with a decreased MFT, but the coated film obtained from the
emulsion showed poor resistance to water and poor surface
hardness.
Comparative Example 11 is one in which the weight average molecular
weight of the shell polymer was increased, where the shell polymer
had insufficient alkali solubility, and can no longer reduce the
MFT of an emulsion containing this powdery material.
Examples 9-12 and Comparative Examples 3-5, 12, and 15-17 are those
of core polymers and shell polymers with different Tg's.
Comparative Examples 3-4 are cases in which the core polymers have
higher Tg's. In these cases, no blocking of the powdery material to
itself are observed, but emulsions containing the resultant powdery
materials end up with MFTs exceeding 20.degree. C. Good
hardenability is shown (Comparative Example 3) if a concrete
product is obtained at 25.degree. C., but the hardenability level
is insufficient for the formation of a concrete product at
5.degree. C., resulting in an incompletely hardened product
(Comparative Example 4).
Comparative Examples 5 and 15 are those in which the Tg's of the
shell polymer are decreased. In these cases, the shell polymers
have Tg's which are too low, so that they block when spray dried,
failing to give powdery products.
Comparative Example 16 is one where the shell Tg is raised. No
blocking of the powdery material to itself is observed, but an
emulsion containing the resultant powdery material has an MFT
exceeding 20.degree. C.
Comparative Example 17 is one where the shell polymer used has a
high Tg, high acid value, and a low molecular weight. In this case,
the state of spray drying is good, giving a powdery product with a
low average particle size, but the cement milk containing the
powdery material has high viscosity and has the MFT raised to
25.degree. C., resulting in a concrete product with poor resistance
to water, resistance to acid, and surface hardness.
Examples 13-15 and Comparative Examples 8 and 9 are cases in which
the average molecular weight of the shell polymer was varied.
Examples 13-15 both give an MFT at 5.degree. C., yielding cement
milk products with good properties and concrete products with good
properties as obtained by hardening the same.
However, Comparative Example 8 in which the weight average
molecular weight of the shell polymer was decreased, gave a powdery
product which did not block and gave an emulsion with decreased
MFT, but generated a coated film from the emulsion which was poor
in resistance to water and resistance to acid.
Comparative Example 9 is one for a shell polymer with an increased
weight average molecular weight, but in this case, the shell had
insufficient alkali solubility so that it could not lower the MFT
of the emulsion containing such a powdery material.
It also increased the viscosity of the cement milk causing inferior
workability.
Comparative Example 12 in which the core polymer had too low a Tg,
undergoing a blocking with the powdery material itself.
Example 20
A 2 l 4-necked flask was charged with 925 parts of water, 12.5
parts of polyoxyethylene nonylphenyl ether (manufactured by Kao KK,
Emarugen 910), and 2.25 parts of potassium persulfate, sparged with
nitrogen, stirred at 130 rpm under a nitrogen gas stream, and
heated to 70.degree. C. Then a monomer mixture of 125 parts of
methyl methacrylate, 125 parts of butyl acrylate, 5 parts of sodium
dioctyl sulfosuccinate (manufactured by Kao KK, Perex OTP) was
added dropwise [to the flask] over 2 hours and the mixture held 1
hour at 70.degree. C. to carry out a first stage emulsion
polymerization. The resultant emulsion had monodispersed particles
with an average particles size of 280 nm. Then a monomer mixture of
135 parts of methyl methacrylate, 65 parts of butyl acrylate, and
50 parts of methacrylic acid was added dropwise in 2 hours, and the
mixture was held 1 hour at 70.degree. C. and then raised to
80.degree. C., and held 1 hour at 80.degree. C. to complete a
second stage emulsion polymerization to give a milky white
emulsion. The resultant emulsion with 36.2% solids was confirmed to
have grown into core-shell structure particles with monodispersed
particles of an average particles size of 350 nm.
Then 2500 parts of the above emulsion was placed in a 2 l 4-necked
flask, stirred at room temperature at 250 rpm, to which was added
dropwise 226 parts of 5% aqueous potassium hydroxide solution in 2
hours. The stirring was continued after completion of the dropwise
addition, where the pH and electrical conductivity were measured
over a period of time until these values no longer changed, at
which time the operation was stopped and the neutralization was
completed giving a milky white neutralized emulsion.
The resultant neutralized emulsion was then spray dried using a
spray dryer (manufactured by Ohkawara Kakoki, L-8 Model) with the
inlet temperature of the spray dryer column set at 150.degree. C.,
the outlet temperature at 80.degree. C., the number of atomizer
revolutions at 30000 rpm, to form a powdery material. The state of
spraying was good in this spray drying operation and there was no
adhesion of the powder to the inner walls of the spray dryer
column. The resultant powder with an average particle size of 26
.mu.m and a residual water content of 1.6% did not show any
blocking of the powdery material to itself at all.
The resultant powder was observed under an electron microscope to
confirm that the powdery material formed had an average particle
size of 26 .mu.m by a secondary aggregation of primary particles
having a particle size of not more than 1 .mu.m.
When this powdery material was added to water, it gave a powdery
material dispersed in the water having an average particle size of
0.65(, confirming that the secondary aggregated particle mass had
dispersed in water, regenerating primary particles, where no
particle or mass with an average particle size exceeding 1 .mu.m
resulted from secondary aggregates.
Table 2 shows the composition of the core polymers and shell
polymers of the resultant powdery materials, along with their Tg,
acid value, core-shell weight ratio, shell molecular weight, and
degree of neutralization. The resultant powdery materials were
evaluated as to their spray conditions in their manufacturing
steps, their anti-blocking properties, dispersion stability, MFT,
and resistance to water, as given in Table 2.
The resultant powdery materials were used as cement modifiers to be
blended with cementitious material under the blend compositions
given below, followed by mixing the mixture for 10 minutes in a
mortar mixer to obtain a cement milk, which was then cured
according to JIS A6203 to prepare concrete products.
Evaluations in the production of concrete products and evaluation
of concrete products themselves were made and the results are given
in Table 2.
Cement Blend Composition A (For troweling) Regular Portland cement
100 parts Sand (Toyoura Standard Sand) 300 parts Cement modifier 10
parts Water 70 .+-. .alpha. parts (.alpha. is freely adjusted)
Cement Blend Composition A (For troweling) Regular Portland cement
100 parts Sand (Toyoura Standard Sand) 300 parts Cement modifier 10
parts Water 70 .+-. .alpha. parts (.alpha. is freely adjusted)
Examples 21-25 and Comparative Examples 18-28
Core-shell structured powdery materials were obtained under
conditions given in Table 2 in a manner similar to that of Example
20. Table 2 shows the composition of the core polymer and shell
polymer of the powders obtained, along with their Tg, acid value,
core polymer/shell polymer weight ratio, the molecular weights of
the core polymer and shell polymer and the extent of
neutralization.
Table 2 also shows the results of evaluating the state of spraying
in the manufacturing steps, the anti-blocking properties,
dispersion stability, MFT and resistance to water, as well as the
results of evaluating the steps to produce concrete products, as
well as the results of evaluating concrete products.
Table 2 also shows the result of evaluating a case with no cement
modifier blended in as a reference example.
Comparative Example 20, Comparative Example 24 and Comparative
Example 26, because of their low shell ratios, low shell Tg's, low
core Tg's, yielded fused products accumulating at the time of spray
drying, which caused blocking or inability to form powder, so that
any subsequent evaluations were not carried out.
Examples 20-22 and Comparative Examples 20 and 21 are cases in
which the core-shell polymerization ratios were changed: Examples
20-22 caused no blocking of the powdery material, gave good
dispersion stability, and showed MFTs at 5.degree. C. or lower and
gave good physical properties when blended into cementitious
material, producing superior physical properties to those without
the powdery material of this invention being blended in (reference
examples). If the shell ratio was too low (Comparative Example 20),
the coating properties of the low Tg core became insufficient,
making it difficult to spray dry, and the resultant powder easily
blocked; if the shell ratio was too high (Comparative Example 21),
the alkali soluble shell increased, resulting in an increased
viscosity when blended into cement, which seriously decreased
workability.
Example 23 and Comparative Examples 18 and 19 are cases in which
the extent of neutralizing carboxyl groups was changed: Example 23
produced a powdery material with no blocking and with good
dispersion stability, but if the degree of neutralization was low
(Comparative Example 18), there was a slight blocking tendency and
it provided no improvement in trowelability and adhesion strength
while a high degree of neutralization (Comparative Example 19) gave
a powdery material which swelled and exhibited decreased dispersion
stability.
Examples 24 and 25 and Comparative Examples 22 and 23 are cases in
which the acid value of the shell was changed: Examples 24 and 25
do not adversely affect MFT or the viscosity when blended with
cementitious material, but if the acid value is too low
(Comparative Example 22), such a shell decreases in alkali
solubility and fails to provide a low MFT, while if the acid value
is too high (Comparative Example 23), the dispersion stability
drops and the viscosity of the cement milk increases, thusly
workability being deteriorated.
Comparative Example 24 is a case where the weight average molecular
weight of the shell is low, resulting in a powdery material with
the resin itself having reduced resistance to water, while
Comparative Example 27 is a case in which the core has a high Tg,
which considerably increases the viscosity of the cement milk.
Comparative Example 25 is a case in which the molecular weight of
the shell was reduced where the resultant cement milk could not
have its MFT reduced to 5.degree. C. or lower, but gave a concrete
product with insufficient resistance to water.
Comparative Example 27 is a case in which the core had an increased
Tg and gave a good spraying state, giving a powdery material, but
its MFT was high at 30.degree. C., causing the viscosity of the
cement milk containing this to increase.
Comparative Example 28 is a case for a product with an elevated
acid value, where the MFT of the cement milk obtained therefrom can
be set to 5.degree. C. or lower, but it gives poor adhesion in a
troweling applications.
Industrial Potential Utility
As discussed above, the powdery material of this invention is
useful as a modifier for cementitious material.
TABLE 1 (Examples for systems with no alkaline neutralization)
Weight Composition of cement modifiers average Core section Shell
section Core/ molecular Compositional Compositional shell weight
State Particle ratio Acid ratio Acid weight (10000) of size
MMA/BA/MAA Tg value MMA/BA/MMA Tg value ratio Core Shell spraying
(nm) Example 1 50/50/0 11 0 54/26/20 59 120 50/50 60 80
.smallcircle. 350 Example 2 50/50/0 11 0 54/26/20 59 120 50/50 60
80 .smallcircle. 350 Example 3 50/50/0 11 0 54/26/20 59 120 50/50
60 80 .smallcircle. 350 Example 4 50/50/0 11 0 54/26/20 59 120
60/40 60 80 .smallcircle. 350 Example 5 50/50/0 11 0 54/26/20 59
120 60/40 60 80 .smallcircle. 350 Example 6 50/50/0 11 0 60/25/15
59 90 50/50 60 80 .smallcircle. 360 Example 7 50/50/0 11 0 54/26/20
59 120 50/50 30 80 .smallcircle. 350 Example 8 50/50/0 11 0
54/26/20 59 120 50/50 100 80 .smallcircle. 355 Example 9 33/67/0
-15 0 54/26/20 59 120 50/50 60 80 .smallcircle. 350 Example 10
41/59/0 0 0 54/26/20 59 120 50/50 60 80 .smallcircle. 350 Example
11 49/50/1 12 6 54/26/20 59 120 50/50 60 80 .smallcircle. 350
Example 12 46/5l/3 11 18 54/26/20 59 120 50/50 60 80 .smallcircle.
350 Example 13 50/50/0 11 0 54/26/20 59 120 50/50 60 30
.smallcircle. 350 Example 14 50/50/0 11 0 54/26/20 59 120 50/50 60
50 .smallcircle. 350 Example 15 50/50/0 11 0 54/26/20 59 120 50/50
60 150 .smallcircle. 350 Example 16 50/50/0 11 0 49/31/20 50 120
50/50 60 80 .smallcircle. 350 Example 17 50/50/0 11 0 60/20/20 72
120 50/50 60 80 .smallcircle. 350 Example 18 50/50/0 11 0 69/11/20
92 120 50/50 60 80 .smallcircle. 350 Example 19 50/50/0 11 0
69/23/8 59 48 50/50 60 80 .smallcircle. 370 Comparative Example 1
50/50/0 11 0 54/26/20 59 120 90/10 60 80 x 350 Comparative Example
2 50/50/0 11 0 54/26/20 59 120 10/90 60 80 .smallcircle. 350
Comparative Example 3 64/36/0 32 0 54/26/20 59 120 50/50 60 80
.smallcircle. 350 Comparative Example 4 64/36/0 32 0 54/26/20 59
120 50/50 60 80 .smallcircle. 350 Comparative Example 5 50/50/0 11
0 38/42/20 32 120 50/50 60 80 x 350 Comparative Example 6 50/50/0
11 0 77/21/2 59 12 50/50 60 80 .smallcircle. 370 Comparative
Example 7 50/50/0 11 0 38/29/33 59 200 50/50 60 80 .smallcircle.
330 Comparative Example 8 50/50/0 11 6 54/26/20 59 120 50/50 60 1
.smallcircle. 350 Comparative Example 9 50/50/0 11 0 54/26/20 59
120 50/50 60 250 .smallcircle. 350 Comparative Example 10 50/50/0
11 0 54/26/20 59 120 50/50 5 80 .smallcircle. 350 Comparative
Example 11 50/50/0 11 0 54/26/20 59 120 50/50 250 80 .smallcircle.
350 Comparative Example 12 16/84/0 -30 0 54/26/20 59 120 50/50 60
80 x 350 Comparative Example 13 40/52/8 11 42 54/26/20 59 120 50/50
60 80 .smallcircle. 350 Comparative Example 14 30/54/16 11 96
54/26/20 59 120 50/50 60 80 .smallcircle. 350 Comparative Example
15 50/50/0 11 0 40/40/20 35 120 50/50 60 80 x 350 Comparative
Example 16 50/50/0 11 0 75/5/20 106 120 50/50 60 80 .smallcircle.
350 Comparative Example 17 50/50/0 11 0 57/10/33 103 200 50/50 5 2
.smallcircle. 100 MFT Properties of (.degree. C.) cement of
Properties of Cement blend composition A modifiers alkaline coated
film Hardening Anti- re- Resistance conditions blocking Re-
dispersed Water to Surface Temperature W/C P/C properties
dispersibility solution resistance acid Viscosity hardness
(.degree. C.) (%) (%) Example 1 .smallcircle. .smallcircle. 5
.smallcircle. .smallcircle. .smallcircle. .smallcircle. 25 55 3
Example 2 .smallcircle. .smallcircle. 5 .smallcircle. .smallcircle.
.smallcircle. .smallcircle. 5 55 3 Example 3 .smallcircle.
.smallcircle. 5 .smallcircle. .smallcircle. .smallcircle.
.smallcircle. 5 55 10 Example 4 .smallcircle. .smallcircle. 5
.smallcircle. .smallcircle. .smallcircle. .smallcircle. 25 55 3
Example 5 .smallcircle. .smallcircle. 5 .smallcircle. .smallcircle.
.smallcircle. .smallcircle. 5 55 3 Example 6 .smallcircle.
.smallcircle. 5 .smallcircle. .smallcircle. .smallcircle.
.smallcircle. 25 55 3 Example 7 .smallcircle. .smallcircle. 5
.smallcircle. .smallcircle. .smallcircle. .smallcircle. 5 55 3
Example 8 .smallcircle. .smallcircle. 5 .smallcircle. .smallcircle.
.smallcircle. .smallcircle. 5 55 3 Example 9 .smallcircle..DELTA.
.smallcircle. 5 .smallcircle. .smallcircle. .smallcircle.
.smallcircle. 5 55 3 Example 10 .smallcircle. .smallcircle. 5
.smallcircle. .smallcircle. .smallcircle. .smallcircle. 5 55 3
Example 11 .smallcircle. .smallcircle. 5 .smallcircle.
.smallcircle. .smallcircle. .smallcircle. 5 55 3 Example 12
.smallcircle. .smallcircle. 5 .smallcircle. .smallcircle.
.smallcircle. .smallcircle. 5 55 3 Example 13 .smallcircle.
.smallcircle. 5 .smallcircle. .smallcircle. .smallcircle.
.smallcircle. 5 55 3 Example 14 .smallcircle. .smallcircle. 5
.smallcircle. .smallcircle. .smallcircle. .smallcircle. 5 55 3
Example 15 .smallcircle. .smallcircle. 5 .smallcircle.
.smallcircle. .smallcircle. .smallcircle. 5 55 3 Example 16
.smallcircle. .smallcircle. 5 .smallcircle. .smallcircle.
.smallcircle. .smallcircle. 5 55 3 Example 17 .smallcircle.
.smallcircle. 10 .smallcircle. .smallcircle. .smallcircle.
.smallcircle. 5 55 3 Example 18 .smallcircle. .smallcircle. 18
.smallcircle. .smallcircle. .smallcircle. .smallcircle. 5 55 3
Example 19 .smallcircle. .smallcircle. 18 .smallcircle.
.smallcircle. .smallcircle. .smallcircle. 5 55 3 Comparative
Example 1 x x -- -- -- -- -- -- -- -- Comparative Example 2
.smallcircle. .smallcircle. .ltoreq.5 .smallcircle. .smallcircle. x
.smallcircle. 5 55 3 Comparative Example 3 .smallcircle.
.smallcircle. 25 .smallcircle. .smallcircle. .smallcircle.
.smallcircle. 25 55 3 Comparative Example 4 .smallcircle.
.smallcircle. 25 .smallcircle. .smallcircle. .smallcircle. x 5 55 3
Comparative Example 5 x x -- -- -- -- -- -- -- -- Comparative
Example 6 .smallcircle. .smallcircle. 50 .smallcircle.
.smallcircle. .smallcircle. x 25 55 3 Comparative Example 7
.smallcircle. .smallcircle. .ltoreq.5 .smallcircle. .smallcircle. x
.smallcircle. 5 55 3 Comparative Example 8 .smallcircle.
.smallcircle. .ltoreq.5 x x .smallcircle. x 5 55 3 Comparative
Example 9 .smallcircle. .smallcircle. 45 .smallcircle.
.smallcircle. x x 25 55 3 Comparative Example 10 .smallcircle.
.smallcircle. .ltoreq.5 x .DELTA. .smallcircle. x 5 55 3
Comparative Example 11 .smallcircle. .smallcircle. 30 .smallcircle.
.smallcircle. .smallcircle. x 5 55 3 Comparative Example 12 x x --
-- -- -- -- -- -- -- Comparative Example 13 .smallcircle.
.smallcircle. .ltoreq.5 x .smallcircle. .DELTA. .smallcircle. 5 55
3 Comparative Example 14 .smallcircle. .smallcircle. .ltoreq.5 x
.smallcircle. x .smallcircle. 5 55 3 Comparative Example 15 x x --
-- -- -- -- -- -- -- Comparative Example 16 .smallcircle.
.smallcircle. 25 x x x x 5 55 3 Comparative Example 17
.smallcircle. .smallcircle. 25 x x x x 5 55 3
TABLE 2 (Examples for systems with alkaline neutralization) Weight
Composition of cement modifiers average Extent Core section Shell
section Core/ molecular of Compositional Compositional shell weight
neutrali- State Particle ratio Acid ratio Acid weight (10000)
zation of size MMA/B.DELTA. Tg value MMA/BA/MA.DELTA. Tg value
ratio Core Shell (%) spraying (nm) Example 20 50/50 11 0 54/26/20
59 120 50/50 60 80 20 0 350 Example 21 50/50 11 0 54/26/20 59 120
70/30 60 80 20 0 350 Example 22 50/50 11 0 54/26/20 59 120 30/70 60
80 20 .smallcircle. 350 Example 23 50/50 11 0 54/26/20 59 120 50/50
60 80 50 .smallcircle. 350 Example 24 50/50 11 0 48/27/25 59 150
50/50 55 80 20 .smallcircle. 320 Example 25 50/50 11 0 67/23/10 59
60 50/50 64 80 20 .smallcircle. 370 Comparative Example 18 50/50 11
0 54/26/20 59 120 50/50 60 80 0 .smallcircle. 350 Comparative
Example 19 50/50 11 0 54/26/20 59 120 50/50 60 80 80 .smallcircle.
350 Comparative Example 20 50/50 11 0 54/26/20 59 120 95/5 60 80 20
x 350 Comparative Example 21 50/50 11 0 54/26/20 59 120 10/90 60 80
20 .smallcircle. 350 Comparative Example 22 50/50 11 0 77/21/2 59
12 50/50 70 80 20 .smallcircle. 370 Comparative Example 23 50/50 11
0 28/32/40 59 240 50/50 49 80 20 .smallcircle. 300 Comparative
Example 24 50/50 11 0 44/36/20 40 120 50/50 60 80 20 .DELTA. 350
Comparative Example 25 50/50 11 0 54/26/20 59 120 50/50 60 3 20
.smallcircle. 350 Comparative Example 26 *1 -45 0 54/26/20 59 120
50/50 60 80 20 x 350 Comparative Example 27 66/34 36 0 54/26/20 59
120 50/50 60 80 20 .smallcircle. 350 Comparative Example 28 *2 11
60 54/26/20 59 120 50/50 60 80 20 .smallcircle. 350 Reference
Example 1 No cement modifier MFT Properties of (.degree. C.) Cement
blend cement of composition B Cement blend composition A modifiers
alkaline Wa- Tro- Strength Strength Anti- Re- re- ter wel- Strength
(25.degree. C.) (5.degree. C.) blocking dispers- dispersed resis-
abi- Flex- Compre- Adh- Visc- Flex- Compre- Flex- Compre-
properties ibility solution tance ility ural ssion esion osity ural
ssion ural ssion Example 20 .smallcircle. .smallcircle. .ltoreq.5
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. Example 21 .smallcircle. .smallcircle.
.ltoreq.5 .smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. Example 22 .smallcircle. .smallcircle.
.ltoreq.5 .smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. Example 23 .smallcircle. .smallcircle.
.ltoreq.5 .smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. Example 24 .smallcircle. .smallcircle.
.ltoreq.5 .smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. Example 25 .smallcircle. .smallcircle.
12 .smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. Comparative Example 18 .DELTA. .DELTA.
.ltoreq.5 .smallcircle. x .smallcircle. .smallcircle. x .DELTA.
.smallcircle. .smallcircle. .smallcircle. .smallcircle. Comparative
Example 19 .smallcircle. .DELTA. .ltoreq.5 .smallcircle.
.smallcircle. .DELTA. .DELTA. .smallcircle. .smallcircle. .DELTA.
.DELTA. .DELTA. .DELTA. Comparative Example 20 x x -- -- -- -- --
-- -- -- -- -- -- Comparative Example 21 .smallcircle. .DELTA.
.ltoreq.5 .DELTA. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. x .DELTA. .DELTA. .DELTA. .DELTA. Comparative Example
22 .DELTA. .DELTA. 40 .smallcircle. .DELTA. .DELTA. .DELTA. x
.smallcircle. .DELTA. .DELTA. x x Comparative Example 23 .DELTA.
.DELTA. .ltoreq.5 .DELTA. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. x .DELTA. .DELTA. .DELTA. .DELTA. Comparative Example
24 x x -- -- -- -- -- -- -- -- -- -- -- Comparative Example 25
.smallcircle. .smallcircle. .ltoreq.5 x .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .DELTA. .DELTA. Comparative Example 26 x x -- -- --
-- -- -- -- -- -- -- -- Comparative Example 27 .smallcircle.
.smallcircle. 30 .smallcircle. .smallcircle. .DELTA. .DELTA.
.DELTA. .smallcircle. .DELTA. .DELTA. x x Comparative Example 28
.smallcircle. .DELTA. .ltoreq.5 .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. x .smallcircle.
.smallcircle. .smallcircle. .smallcircle. Reference Example 1 No
cement modifier x .smallcircle. .smallcircle. .DELTA. .smallcircle.
.DELTA. .DELTA. x x *1: BA = 100 *2: MMA/BA/MAA = 38/52/10 The
symbols in the tables are as given below; MMA: methyl methacrylate
BA: butyl acrylate MAA: mathacrylic acid W/C: water/cementitious
material .times. 100% P/C: powdery material/cementitious material
.times. 100%
* * * * *